The present invention relates to treatment of tissue. More particularly, the present invention provides methods and apparatus for treating valvular disease with a catheter inserted into a patient""s cardiac chambers, the catheter having an end effector for modifying cardiac structures, including valve leaflets and support structure.
Degenerative valvular disease is the most common cause of valvular regurgitation in human beings. Regurgitation is typically characterized by an expanded valve annulus or by lengthened chordae tendineae. In either case, an increase in the geometry of a valve or its supporting structure causes the valve to become less effective, as it no longer fully closes when required.
Loose chordae tendineae may result, for example, from ischemic heart disease affecting the papillary muscles. The papillary muscles attach to the chordae tendineae and keep the leaflets of a valve shut. Some forms of ischemic cardiac disease cause the papillary muscles to lose their muscle tone, resulting in a loosening of the chordae tendineae. This loosening, in turn, allows the leaflets of the affected valve to prolapse, causing regurgitation.
It therefore would be desirable to provide methods and apparatus for treatment of tissue that modify the geometry and operation of a heart valve.
It would also be desirable to provide methods and apparatus that are configured to thermally treat chordae tendineae, the annulus of a valve, or valve leaflets.
It would also be desirable to further provide methods and apparatus that are configured to mechanically modify the geometry and operation of a heart valve and annulus of a valve either alone or in addition to thermal treatment.
In view of the foregoing, it is an object of the present invention to provide methods and apparatus for the treatment of tissue that modify the geometry and operation of a heart valve.
It is another object of the present invention to provide methods and apparatus that are configured to thermally treat chordae tendineae, the annulus of a valve, or valve leaflets.
It is another object of the present invention to further provide methods and apparatus that are configured to mechanically modify the geometry and operation of a heart valve and annulus of a valve either alone or in addition to thermal treatment.
These and other objects of the present invention are accomplished by providing apparatus and methods for thermally or mechanically treating tissue, such as valvular structures, to reconfigure or shrink the tissue in a controlled manner, thereby improving or restoring tissue function. Embodiments of the present invention advantageously may be employed to modify flow regulation characteristics of a cardiac valve or its component parts, as well as to modify flow regulation in other lumens of the body, including, for example, the urinary sphincter, digestive system valves, leg vein valves, etc., where thermal shrinkage or mechanical reconfiguration of tissue may provide therapeutic benefit.
In a first family of embodiments of the present invention, apparatus is provided having an end effector that induces a temperature rise in an annulus of tissue surrounding the leaflets of a valve sufficient to cause shrinkage of the tissue, thereby reducing a diameter of the annulus and causing the valves to close more tightly. In a second family of embodiments, apparatus is provided having an end effector that selectively induces a temperature rise in the chordae tendineae sufficient to cause a controlled degree of shortening of the chordae tendineae, thereby enabling the valve leaflets to be properly aligned. In yet a third family of embodiments, apparatus is provided having an end effector comprising a mechanical reconfigurer configured to attach to a longitudinal member, such as the chordae tendineae. The reconfigurer forces the longitudinal member into a tortuous path and, as a result, reduces the member""s effective overall or straight length.
Any of these embodiments may employ one or more expanding members that serve to stabilize the end effector in contact with the tissue or structure to be treated. In addition, where it is desired to preserve the interior surface of a lumen or structure, the instrument may include means for flushing the surface of the tissue with cooled saline. Where it is desired to achieve a predetermined degree of heating at a depth within a tissue or structure, the end effector may comprise a laser having a wavelength selected to penetrate tissue to the desired depth, or the end effector may comprise a plurality of electrically conductive needles energized by an RF power source, as is known in the electrosurgical arts. The end effector may alternatively comprise an acoustic heating element, such as an ultrasonic transducer.
In another aspect of the present invention, mechanical clips may be provided preferably made from shape memory alloys or superelastic alloys, e.g., Nickel-Titanium alloy (nitinol). Such clips may be delivered to the valve and annulus of tissue surrounding the valve in a variety of ways, e.g., intravascularly, endoscopically, or laparoscopically, either after the thermal treatment described above, or without the thermal treatment. During delivery by, e.g., a catheter, the clips may be compressed into a smaller configuration to facilitate transport. Upon exiting the catheter, the clips preferably expand to a second configuration for attachment to the valve tissue. The clips may be attached to the annulus of tissue surrounding the valve upon being urged out of the catheter distal end; they may be attached to opposing sides of the valve and preferably have a compressive spring force to draw or cinch the sides of the valve towards one another. The clips may be configured to traverse directly over the valve itself, but they are preferably configured to lie partially over the periphery of the valve to prevent obstruction of the valve channel. A central region of the clips may be formed in a variety of geometric shapes, e.g., semi-circles, arcs, half-ellipses, triangles, rectangles, and loops. Aside from clips, expandable meshes and grids may also be used to draw or cinch the valve edges together.
Moreover, the clips may be coated with therapeutic drugs, which may be time-released, or they may also be coated at least partially with a radiopaque coating to aid in visualization during implantation.
Delivery catheters which may be used to deliver the clips may also incorporate sensors or energy delivery devices, e.g., transducers, on the distal ends. For example, they may be configured as a sensor to measure properties, e.g., ultrasound, Doppler, electrode, pressure sensor or transducer, etc., of the tissue prior to catheter withdrawal. Such sensors may also be used to measure properties such as flow rates, pressure, etc. for measurement pre-treatment and post-treatment. Alternatively, they may also be used as a transducer to deliver energy, e.g., RF, electrical, heat, etc., to the affected tissue or the surrounding area by, e.g., either as a separate device or directly through the clip itself.
Methods of using apparatus according to the present invention are also provided.